The 1977 Chicago Loop derailment occurred on February 4, 1977, when a Chicago Transit Authority elevated train rear-ended another on the northeast corner of the Loop at Wabash Avenue and Lake Street during the evening rush hour. The collision forced the first four cars of the rear train off the elevated tracks, killing 11 people and injuring at least 268 as the cars fell onto the street below. Infrastructure layout "The Loop" not only refers to Chicago's central business district, but also a rectangular pattern formed by the city's elevated trains. Some trains entering the Loop do a complete circuit around the entire rectangular "loop", and after turning around all four corners, leave on the same path they came from. Other routes enter the Loop, turning only two of the corners, and then leave on a different route. Further complicating this is the fact that some trains' routes follow a clockwise pattern around the Loop, but others go counter-clockwise. In 1977, when the crash occurred, there were four lines operating on the Loop, each in a different direction. The Ravenswood Line (current Brown Line) operated counter-clockwise around the outer track, while the Evanston Express (current Purple Line) and Loop Shuttle operated clockwise opposite from the Ravenswood trains on the inner track. The Lake–Dan Ryan Line (part of the current Green Line) operated in both directions, but only using the Lake and Wabash legs of the Loop. Earlier in the day of the accident, a switching issue forced dispatchers to reroute the Evanston Express to run counter-clockwise around the Loop instead of its normal clockwise route. This put it on the tracks normally used by the Ravenswood and westbound Lake–Dan Ryan trains. Because of congestion caused by this abnormal track sharing, the Ravenswood train would be required to stop short, waiting for the rerouted Evanston Express to clear before proceeding. Additionally, this delay meant that the Ravenswood was still in place when the Lake–Dan Ryan train arrived on these tracks, and it too was required to stop and wait for the Ravenswood to clear the track before proceeding. Collision At about 5:25 p.m., a Ravenswood train was waiting on the tracks, just past the northeast turn, waiting for the Evanston Express to clear the State/Lake platform. However, the Lake–Dan Ryan train did not stop as it approached the Ravenswood train. The Lake-Dan Ryan train proceeded against both track and cab signals